O modo de CPU 'custom' para o domínio x86_64 kvm no host x86_64 não é suportado pelo hipervisor

Question

Eu tenho o mesmo problema que aqui , mas a solução não funciona para mim. Toda vez que eu quero criar ou executar uma VM com o virt-manager, recebo a mesma mensagem:

Error al iniciar dominio: configuración no soportada: CPU mode 'custom' for x86_64 kvm domain on x86_64 host is not supported by hypervisor 

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 89, in cb_wrapper
    callback(asyncjob, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 125, in tmpcb
    callback(*args, **kwargs)
  File "/usr/share/virt-manager/virtManager/libvirtobject.py", line 82, in newfn
    ret = fn(self, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/domain.py", line 1508, in startup
    self._backend.create()
  File "/usr/lib/python2.7/site-packages/libvirt.py", line 1069, in create
    if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirtError: configuración no soportada: CPU mode 'custom' for x86_64 kvm domain on x86_64 host is not supported by hypervisor 

No entanto, ao aplicar a correção do thread de menções, obtenho:

Error al iniciar dominio: internal error: process exited while connecting to monitor: Could not access KVM kernel module: Permission denied
2018-03-13T22:43:10.555542Z qemu-system-x86_64: failed to initialize KVM: Permission denied

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 89, in cb_wrapper
    callback(asyncjob, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 125, in tmpcb
    callback(*args, **kwargs)
  File "/usr/share/virt-manager/virtManager/libvirtobject.py", line 82, in newfn
    ret = fn(self, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/domain.py", line 1508, in startup
    self._backend.create()
  File "/usr/lib/python2.7/site-packages/libvirt.py", line 1069, in create
    if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirtError: internal error: process exited while connecting to monitor: Could not access KVM kernel module: Permission denied
2018-03-13T22:43:10.555542Z qemu-system-x86_64: failed to initialize KVM: Permission denied

Eu também tentei como root, mas mesmo resultado.

Meu sistema é Parabola GNU / Linux-libre (baseado em Arch) x86_64